Proteins on SDS-PAGE running down & then up!?!

Natasha Schokman dear_natasha at
Fri Apr 19 11:12:27 EST 2002


I have been running whole cell lysates from mouse 3T3
fibroblasts using SDS-PAGE for over a year now.  But
recently I have encountered the problem where for some
unknown reason my pre-stained markers indicate that my
148 kDa marker band (which is stained orange) is
starting to migrate upwards above my 250 kDa marker
band (which is stained blue).  The puzzling fact is
that the rest of the markers below this point indicate
that the rest of the gel has run fine as all the other
smaller markers separate out fine.  

Overnight transferring to a nitrocellulose membrane
and Ponceau red staining indicates that there is no
protein from ~130 kDa - top of the gel region. 
However, the rest of the proteins from 130 kDa and
smaller have separated properly.  Unfortunately for
me, my protein of interest is 140 kDa!

Any suggestion as to why this is happening would be


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